Snails can tell you how you're managing your tank. A few snails tell you you're feeding the right amount. If the snail population is getting a little out of control, you're feeding too much. Reduce the amount you feed and change the water more often and vacuum the bottom material to remove excess nutrients.
Snails are a good thing. They clean up after the fish and when they die, their shells dissolve in the tank water and replenish elements the fish and plants need for good health.
"Fear not, my young apprentice. Just change the tank water."